Effect of $$\gamma $$ γ -irradiation on the thermal properties of UHMWPE/MWCNTs nanocomposites: a comparative study of incorporating unmodified and $$\gamma $$ γ -ray-modified MWCNTs

Abstract

The efficacy of defective sites in MWCNTs as free radical scavengers was investigated on the basis of thermal analysis of ultra-high molecular weight polyethylene (UHMWPE)/MWCNTs and UHMWPE/γ-MWCNTs nanocomposites. Homogenized composites of polyethylene (PE) with MWCNTs and γ-MWCNTs (0.5% by weight) were prepared by the ball milling process for 2 h at a speed of 200 rpm. Thereafter, micron-sized sheets were prepared (by hot pressing) and subjected to γ-dose ranging from 25 to 150 kGy. To investigate the thermal properties and thermal stability, differential scanning calorimetric (DSC) and thermo-gravimetric analysis (TGA) measurements were performed in an inert atmosphere. The results showed that peak melting temperature (T m) and lamellae thickness (L c) remained unaltered for UHMWPE/MWCNTs composites; however, for UHMWPE/γ-MWCNTs composites the values varied from 138 to 141 • C. This behaviour was attributed to chain scission close to crystalline lamellae due to radiation-induced free radicals, thus reducing the percentage of inter-phase contents within the polymer matrix and enhancing the percentage crystallinity for composites. Furthermore, TGA revealed the higher thermal stability of composites as compared with pristine ones and significant increase in residues percentage for composites, i.e., from ∼ 3 to 7%. These results confirmed the importance of defective sites within the MWCNTs as free radical quenchers, and stopping the chain scission, particularly close to crystalline lamellae, thus preventing loss of the important interphase region of UHMWPE.

In situ fabrication of CuO/UHMWPE nanocomposites and their tribological performance

“…In nano‐CuO/UHMWPE composites, CuO nanofiller with a higher degree of crystallinity than UHMWPE are highly dispersed in the melted UHMWPE. When the temperature of the melted mixture of UHMWPE and nano‐CuO decreases, the CuO nanofiller with a high surface energy could provide a place for the nucleation of UHMWPE, leading to an enhancement in the degree of crystallinity of the matrix . Therefore, the CuO crystal filled in UHMWPE can promote the crystallization of the matrix UHMWPE, indicating a role of heterogeneous nucleation.…”

Gamma-Ray Modified Polymer/Clay Composites: Synthesis, Characterization, and Formulation Optimization Using Multivariate Calculus and Graph Theory

“…Shown in Table 4 are the values of the oxidation index (OI), percent crystallinity (Xc), and crosslinking density for unirradiated and gamma-irradiated PE, PE-SP1, PE-SP2, and PE-SP3, respectively. These values are calculated while using methods explained in the literature for UHMWPE [14][15][16]. The general trend, as far as the radiation of composites is concerned, is as expected-i.e., a decrease in the percent crystallinity due to chain scission close to the crystalline lamellae and an increase in OI as well as Gx because of the aforementioned radiation-induced free radicals' crosslinking and oxidation reactions.…”

“…The spectra were averaged and analyzed for SP and radiation-induced alterations and updates. The values of OI, Xc (%), and Gx were calculated from their respective absorption bands, as reported in the literature [14][15][16]. The data were analyzed with the help of a correlation matrix, CA, and PCA to explore the hidden pattern in the data and establish the correlation among the variables.…”

“…Subsequent to the identification of LOV and HOV factors, their relative importance needed to be established. This is accomplished with the help of expert opinions and documented literature [14][15][16][17]. During the course of this study, experts having experience of more than five years were approached for their opinions and set the relative importance given below:…”

“…An increase in absorption under -CH 2 bending and stretching vibrations with the dose. These are the characteristics of polyethylene absorption bands, and according to reported literature [14][15][16], the ratio of -CH2 bending to stretching vibrations is used as the quantitative measure of crosslink density Gx [16,32].…”